The principle of ink jet recording process is that a liquid or molten solid ink is jetted through a nozzle, slit or porous film to perform recording on a paper, cloth, film, etc. As methods for jetting the ink there have been proposed various methods such as electric charge controlling method which in which an ink is jetted utilizing electrostatic attraction force, drop-on-demand method (pressure pulse method) in which an ink is jetted utilizing the oscillation pressure of a piezoelectric element, and heat ink jet method which comprises utilizing a pressure developed by the thermal formation and growth of air bubbles to jet the ink. These methods can provide an image having an extremely high precision.
As an ink for use in such an ink jet recording process there has been known and used an ink comprising various water-soluble dyes or water-dispersible pigments dissolved or dispersed in water or a liquid medium comprising a water-soluble organic solvent.
Studies have been made for improving the above described conventional ink. The ink for use in ink jet printer has been studied from the following standpoint of requirements:
(1) The ink provides a uniform image having a high definition and a high density and being free of feathering; PA0 (2) The ink does not cause clogging at the tip of nozzles due to drying of the ink and thus always exhibits good jetting response and jetting stability; PA0 (3) The ink quickly dries up on a paper; PA0 (4) The ink provides an image having a good fastness; PA0 (5) The ink exhibits a good storage stability over a long period of time; and PA0 (6) The ink is safe and free of offensive smell.
In order to satisfy these requirements, many proposals have heretofore been made.
In particular, many proposals have heretofore been made to use 2,2'-thiodiethanol. For example, JP-A-61-55546 proposes the combination of a specific dye and a solvent containing 2,2'-thiodiethanol. Further, JP-A-1-263169 proposes the combination of C.I. Direct Black 168 and a specific solvent containing 2,2'-thiodiethanol.
With the use of 2,2'-thiodiethanol, an ink for ink jet recording which causes no clogging at the tip of nozzles and quickly dries up on a paper to provide a sharp image free of feathering, can be obtained. However, the resulting ink is disadvantageous in that 2,2'-thiodiethanol is a sulfur-containing compound having a unique offensive odor. When printing is conducted in large quantities at common offices, houses, etc., the odor presents problems.
Further, since 2,2'-thiodiethanol chemically attacks a member with which the ink comes into contact, particularly resins such as polyimide and polysulfone and rubber material, inks containing 2,2'-thiodiethanol have a problem in its preservability, or are disadvantageous in that it exhibits a remarkably deteriorated jetting stability after storage.
The present invention has been achieved to solve the above described problems in conventional techniques.